Molecular surveillance of European quinolone-resistant clinical isolates of Pseudomonas aeruginosa and Acinetobacter spp. using automated ribotyping

Nosocomial isolates of Pseudomonas aeruginosa and Acinetobacter spp, exhibi t high rates of resistance to antibiotics and are often multidrug resistant . In a previous study (D. Milatovic, A. Fluit, S, Brisse, J, Verhoef, and F , J. Schmitz, Antimicrob. Agents Chemother, 44:1102-1107, 2000), isolates o f these species that were resistant to sitafloxacin, a new advanced-generat ion fluoroquinolone with a high potency and a broad spectrum of antimicrobi al activity, were found in high proportion in 23 European hospitals. Here, we investigate the clonal diversity of the 155 P. aeruginosa and 145 Acinet obacter spp, sitafloxacin-resistant isolates from that study by automated r ibotyping. Numerous ribogroups (sets of isolates with indistinguishable rib otypes) were found among isolates of P. aeruginosa (n = 34) and Acinetobact er spp, (n = 16), but the majority of the isolates belonged to a Limited nu mber of major ribogroups. Sitafloxacin-resistant isolates (MICs > 2 mg/lite r, used as a provisional breakpoint) showed increased concomitant resistanc e to piperacillin, piperacillin-tazobactam, ceftriaxone, ceftazidime, amika cin, gentamicin, and imipenem. The major ribogroups were repeatedly found i n isolates from several European hospitals; these isolates showed higher le vels of resistance to gentamicin and imipenem, and some of them appeared to correspond to previously described multidrug-resistant international clone s of P. aeruginosa (serotype O:12) and Acinetobacter baumannii (clones I an d II). Automated ribotyping, when used in combination with more discriminat ory typing methods, may be a convenient library typing system for monitorin g future epidemiological dynamics of geographically widespread multidrug-re sistant bacterial clones.